Optical connectors are an vital part of any optical fiber communication system. For instance, such connectors may be used to join segments of fiber into longer lengths; to connect optical fibers to active devices such as a radiation sources and detectors; or to connect optical fibers to passive devices such as switches and attenuators. The central function of an optical connector is the maintenance of two optical fiber ends such that the core of one of the fibers is axially aligned with the core of the other fiber; and consequently, all of the light from one fiber is coupled to the other fiber. This is a particularly challenging task when the light-carrying region (core) of an optical fiber is quite small. In singlemode optical fibers, for example, the core diameter is only about 9 microns. Less demanding, although still challenging, are multimode fibers that are made from glass and have fiber core diameters that are typically 50 or 62.5 microns.
Another function of the optical connector is to provide mechanical stability and protection to the junction in its working environment. Achieving low insertion loss in coupling two fibers is generally a function of the alignment of the fiber ends, the width of the gap between the ends, and the optical surface condition of either or both ends. Stability and junction protection is generally a function of connector design (e.g., minimization of the different thermal expansion and mechanical movement effects).
A variety of optical fiber connectors are known in the art, and a discussion of same is provided at pages 301-325 of the textbook entitled Optical Fiber Telecommunications II, which was edited by S. E. Miller and I. P. Kaminow, Academic Press (1988). Optical fiber connectors are typically assembled using a ferrule, which is a solid cylinder having a narrow passageway that extends along its central axis through which a glass or plastic optical fiber is threaded. The ferrule has a circular cross section with the passageway positioned precisely at its centroid, and such precision does not come cheaply. Threading the fiber is normally accomplished by special equipment at a manufacturing location or by a skilled technician in the field. Moreover, adhesive materials are required to hold the fiber within the passageway of the ferrule; and so the use of such ferrules is both inconvenient and expensive.
Optical connectors use a ferrule for alignment and support of the fiber, whether it is made from glass or plastic. A typical example of an optical fiber connector that uses a glass fiber within a ferrule is shown in U.S. Pat. No. 4,934,785. Examples of optical fiber connectors that use a plastic fiber within a ferrule include:
(i) the F07 Duplex Plastic Fiber System from AMP; PA1 (ii) the SMI (Small Multi-media Interface) Connector from Sony Corporation; and PA1 (iii) the HFBR series of plastic fiber connectors from Hewlett Packard.
U.S. Pat. No. 5,719,977 discloses an optical connector having an immovable ferrule, which substantially reduces the cost and complexity of such connectors. However, it still uses a ferrule and still requires a skilled technician to make field installations.
Accordingly, what is desired is a simpler and less-expensive optical connector that overcomes the above limitations and which can be conveniently installed onto an optical cable in the field by a non-skilled person.